Enzymatic changes - new concepts for food sector

Could enzymatic changes in complex carbohydrates improve the nutrient content of food and animal feed? New knowledge from a group of European researchers working on the hydrolytic reactions of glycosidic bonds and their inhibition suggests yes.

The group maintains that their findings will not only benefit processing technologies but also improve the quality of a variety of products.

Enzymatic hydrolysis of complex carbohydrates containing alpha or beta glycosidic bonds is important in nutrition and in several technological processes. These enzymes are called glycosidases (Enzyme Class 3.2.1) and include amylases, pectinases and xylanases. They are present in many foods, such as cereals, but their microbial analogues are often produced and added in many food processes, for instance to improve the shelf-life of bakery products, clear beer, produce glucose, fructose or dextrins, hydrolyse lactose, modify food pectins, or improve processes. Amylase enzymes (which degrade alpha glysosidic bonds) are also produced in the digestive system for starch breakdown.

However, many plant foods also contain endogenous inhibitors which reduce the activity of glycosidases, in particular proteins, peptides, complexing agents and phenolic compounds.

Under the European funded project GEMINI, researchers, led by Dr Nathalie Juge at the Institute of Food Research in Norwich, UK, are focusing on plant proteinaceous inhibitors. Their objectives? To understand these inhibitory reactions and to determine their biodiversity and expression in plants.

Results, the scientists maintain, will contribute to the optimisation of industrial processes by using modified enzymes not influenced by the natural inhibitors. They will also allow careful selection of raw material and reaction conditions, and future development of new genetic varieties low in inhibitors. These, they believe, are all new and promising concepts for the food sector.

The project​ participants have already purified and produced several inhibitors of amylases, xylanases, polygalacturonases and pectin methylesterases. In addition, they have isolated novel inhibitors and target enzymes, determined the X-ray structure of two novel xylanase inhibitors and identified plant genes responsible for the enzyme and for the inhibitor production.

The have also studied the inhibition reaction and found some modified (mutant) xylanases produced from micro-organisms which are independent of the plant inhibitors. Using these inhibitor resistant xylanases in wheat, chicks fed the product utilised the feed more efficiently.

Baking trials are currently underway using reconstituted flour, measuring directly the effect of xylanases and their inhibitors. On a final note, the project is also studying the role of glycosidases and their inhibitors in plant resistance to invading microbia.